Duplex variable electrical resistance device



Nov. 8, 1966 o. BELLAR 3,284,752

DUPLEX VARIABLE ELECTRICAL RESISTANCE DEVICE Filed Oct. 24, 1965 2Sheets-Sheet 1 JA/VEA/T'OP.

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Nov. 8, 1966 o. BELLAR DUPLEX VARIABLE ELECTRICAL RESISTANCE DEVICEFiled Oct. 24, 1965 2 Sheets-Sheet 2 United States Patent 3,284,752DUPLEX VARIABLE ELECTRICAL RESISTANCE DEVICE Oscar Bellar, Alhambra,Calif., assignor to Terence Dalhy, Alhambra, Calif. Filed Oct. 24, 1965,Ser. No. 504,862 9 Claims. (Cl. 338-131) This invention relates tovariable electrical resistance devices and more particularly to animproved form thereof operating on the principle of my copendingapplication Serial No. 504,901, filed October 24, 1965.

The principal object of the invention is: to provide a duplex variableresistance device of the above character in which two separateresistance adjusting means are mounted for movement on a common base andare associated with separate conductor means comprising two resistanceassemblies, also mounted on said common base, which assemblies may beconnected in electrical circuits in different manners, e.g., to serve'as two completely sepa rate variable resistance devices, in which oneof said two devices may be interconnected to modify the output of theother of said devices, in which, for example, one of the devices may beused as a potentiometer device while the other may be used as a rheostatand/or in this latter combination, so that one of the devices may modifythe output of the other device.

Another object of the invention is to provide a device of the abovecharacter which is capable of being made in miniature form or size foruse with very small cur-rent potentials.

Still another object of the invention is to provide a device of theabove character which is small in size, composed of parts which are fewin number and simple in de- Sign, and which is effective for itsintended purposes.

With the foregoing objects in view, together with such additional.objects and advantages as may subsequently appear, the invention residesin the parts and in the con st-ruetion, combination and arrangement ofparts described, by w-ay of example, in the following specification of apresently preferred embodiment of the invention, reference being had tothe accompanying drawings which form a part of said specification and inwhich drawings:

FIG. 1 is a side elevational view of a variable resistance deviceconstituting a presently preferred embodiment of the invention,

'FIGS. 2 and 3 are, respectively, top plan and bottom plane views of thedevice shown in FIG. 1,

FIG. 4 is a transverse medial sectional view taken on the staggered line44 of FIGS. 2 and 3,

FIG. 5 is a fragmentary bottom plan view of a portion of the deviceindicated by the arrowed line 55 of FIG. 4,

FIG. 6 is a transverse sectional plan view taken on the line 6-6 of FIG.4,

FIG. 7 is a fragmentary sectional view taken on the line 77 of FIG. 6,

FIG. 8 is a perspective view of the internal brush component of thedevice,

FIG. 9 is a perspective view of one of the plurality of external brushcomponents of the device, a portion of the actuating means thereforbeing included in the figure,

FIG. 10 is a circuit diagram of the fundamental circuitry of the device,and

FIG. 11 is a schematic view illustrating the arrangement of the wires orconductors of the inner and outer resistance assemblies of the device.

Referring to the drawings, the illustrated embodiment of the inventioncomprises a circular, thick, disc-like nonconductive base 1 having afirst series of three terminals 2a, 2b and 20 extending therethroughparallel to the axial line of the base and disposed at equal radialdistances 3,284,752 Patented Nov. 8, 1966 from said line and at equaldistances from each other, and with a second series of terminals 3a, 3band 3c arranged oppositely with respect to said first series ofterminals but at lesser radial distances from the center of the basewhereby (see FIG. 3) terminal 3a is diametrically opposite terminal 2a,etc. Exteriorly of said base, said terminals are shown as forming socketengaging pins but it will be appreciated that any mode of electricalconnection may be substituted therefor.

The outer periphery of the base 1 is provided with a peripheral groove 4in which a snap ring 5 is disposed; said ring normally extendingoutwardly of said groove and engaging a complementary groove 6 in theinner peripheral surface 7 of a cylindrical body member 8 which closelybut freely rotatably fits the periphery of the base 1. An opening 5 fromthe under side of the base 1 affords access to the ends of the spring 5for a suitable tool for collapsing the spring incident to installationor removal of the body member 8 therefrom, said ring serving to hold thebody and base in assembly.

In the description of the illustrated embodiment of the invention and ofthe various component parts thereof the relationship thereof will bereferred to as being above," below, etc. Since the device may be used inany particular position or attitude, it will be understood that suchdesignation of relationship between parts is merely one of conveniencehaving reference to the illustration thereof. Also, the wire componentsconstituting the resistance assemblies of the device and of the brushcomponents thereof are frequently of only a few thousandths of an inchin diameter wherefore, it will be understood that the showing thereof inthe drawings is to be regarded as schematic in view of the fact that toshow such elements in their true proportion to the rest of the devicewould cause the rest of the device to be shown in such a large scale asto be thoroughly impractical and, in any event, to add nothing to anunderstanding of the invention. In its smaller sizes, the embodimentshown in FIG. 1 for example, would seldom, if ever, exceed about /2 indiameter.

The body 8 extends above the upper face of the base 1 and the exteriorsurface thereof is preferably provided with a suitable surface formanual gripping such as the flutes 9 formed thereon. Alternatively, ofcourse, a series of ribs might be employed or any other configurationthat would be susceptible of economical-manufacture and provide a goodsurface for manual gripping without slippage. The said internal surface7 of the body extends in parallel relation to the side or peripheralsurface of the base 1 for the length of that peripheral surface andthence continues above the upper surface of the base 1 to combine withthe upper surface of the base 1 to form a cavity portion 10 in which thevariable resistance components, per se, are contained. From the topsurface of the base 1 to the upper end of the cavity 10, the saidinternal surface 7 is interrupted by pairs of vertically extending ribmembers 11, 11 which combine to serve as the guiding and actuating meansfor a pair of external brush components 12, 12 to which furtherreference will hereinafter be made.

Mounted on the base 1 within the cavity 10 is the cylindrical resistanceassembly support member 13 comprising a hollow cylindrical member ofnon-conductive ma terial having a reduced diameter rib portion 14 at oneend thereof which engages a groove 15 in the upper surface of the baseand in which groove it is secured by adhesive or any other suitablemeans. The outer diameter of the member 13 is preferably not greaterthan twice the radius of the distance from the center line of the disc 1to the inner or adjacent sides of the outer terminals 2a, 2b and 2c andthe inner diameter of the member 13 is preferably not less than twicethe radius from the center line of the body 1 to the outermost face ofthe inner row of terminals 3a, 3b and 3c. The length of the member 13may be any length that will accommodate the length of the resistanceassemblies carried thereby as will presently appear.

The external surface of the member 13 carries the outer resistanceassembly 16 comprising three wires leading one each from each of theterminals 2a, 2b and 2c laid side by side and in that side-by-siderelation wound in a helix on the outer surface of the member 13 andsecured thereon by any suitable means such as, for example, by suitableadhesive, the said wires having a non-conductive coating so as not to beelectrically interconnected except by the brush means to be presentlydescribed.

Similarly, the internal resistance assembly 17 comprises a series ofthree wires leading from the terminals 3a, 3b and 3c laid side by sideand wound similarly in a helix on the inner surface of the body 13 andadhered thereto by suitable adhesive. In actual practice, these wireswould first be wound on a collapsible mandrel of appropriate diameter sothat the resulting winding would fit closely on the inner diameter ofthe member 13, the resulting winding would be inserted on the innersurface of the member 13 with suitable adhesive and after the adhesivehad set, the mandrel would be collapsed and removed from the windingthus adhered to the inner surface of the member 13. As with the wirescomprising the outer resistance assembly 16, these wires would also 'becoated with nonconductive material so that they could be electricallyinterconnected only by brush means including the brush element orcomponent 18 presently to be described in detail.

Beyond the upper end of the member 13, the body 8 is provided with anend wall 19 having a depending annular flange engaging the upperinterior diameter of the resistance assembly supporting body 13, saidengagement constituting a bearing means in addition to the bearingengagement with the body 1 having an axially disposed opening 20extending therethrough in which the shank 21 of an operating knob 22 forthe inner brush component 18 is mounted for free rotation, said knobbeing restrained against endwise movement in said axial opening 20 by agasket 23 between the knob '22 and the outerupper surface of the endwall 19 and by a snap ring 24 engaging a peripheral groove 25 in theshank 21 at the inner side of the end wall 19. The shank 21 of the handknob 22 carries a depending non-circular shank 26 which engages acomplementary hole 27 in a sheet metal retainer 28 for the contactelement 29 of the internal brush component 18 whereby rotation of theshank 26 by the knob 22 and consequent rotation of the brush component18 will allow the brush component to move longitudinally of the shank ina manner and for a purpose presently to be described.

Each of the external brush assemblies 12 comprises an elongated basemember 30 generally conforming to the curved surface 7 of the body 8 andextending between the opposed faces of one of the pairs of ribs 11, 11.At each end thereof, it is provided with a radially inwardly extendingportion 31 and mounted on the members 31, 31 and secured thereby by caps31', 31' adhered thereto and to the member 30 are small metal blocks 32,32 which are united with the respective opposite ends of the series ofspring wires 33 which, in effect, extend as the center portion of thechord of an are represented by the curvature of the member 30 and whichwires, in a line radially of the axial line of the resistance assembly16, normally are disposed at a lesser distance than said radialdimension wherefore, when brought into contact with the exterior of theouter resistance assembly, they are slightly outwardly bowed to producea light but definite and continuous yielding engagement with the wiresof the outer resistance assembly 16 as best indicated in FIG. 6. Thewires 33 are uninsulated wires and the outer surfaces of the wiresconstituting the outer resistance assembly 16 have had the coatingthereof removed so that the contact with the wires 33 will be anelectrically conductive contact. Moreover, the wires 33 are preferablyof approxiguiding ways formed by adjacent pairs of the ribs 11, 11. l

The contact element 29 of the internal brush assembly 18 comprises ahelical spring which, as best shown in FIGS. 6 and 8 is deformed byinwardly curving the spring at three portions thereof as indicated at 34leaving contact surfaces or portions 35 which normally are of slightlygreater radial dimension than the least radial dimension of the internalresistance assembly 17. The supporting and driving member 28 comprises asheet of metal having three laterally extending arm portions 36 whichextend from beneath the member 29 loosely eX- teriorly of the inwardlycurved portions 34 and thence overlap said portions with inturned lips37. Thus, the radial inward compression of the contact portions 35 uponengagement with the inner resistance assembly 17 will be accommodated byslight inward bowing of the portions 34, the resilience of which assurescontinuous yielding contact with the internal surface of the internalresistance assembly 17. The wires 33 are preferably of approximately thesame diameter wires as constitute the resistance assembly with whichthey are in contact so that they will engage the grooves formed byadjacent wires with the result that rotation of the brush element willcause it to engage the said grooves as though said grooves constituted ahelical thread and to be moved axially of said resistance assembly inthe direction and to the extent determined by the rotation of the brushelement.

As previously mentioned, this device is capable of a wide variety ofuses. Assuming for example, that the wires of the outer resistanceassembly associated with terminals 2a and 212' are connected in a seriescircuit, the movement of the brush element 12 across the resistanceassembly will vary the resistance dependent on the number of turns ofthe resistance assembly between the brush component and the terminal.Thus far assuming that the terminal 2c is not connected in any circuit,the outer resistance assembly and brush will act as a simple rheostat.

Next assuming that the terminal 2c and the wire of the resistanceassembly associated therewith is connected to some other portion of acircuit, the outer resistance assembly and its associated brush means asadjusted by rotation of the body 8 operates as a potentiometer varyingthe current supplied to terminal 2c.

What has been said with respect to two possible uses of the outerresistance assembly is equally true of the inner resistance assembly andits adjustable brush component 18. Any two of the three wires may serveas a simple rheostat device while with the third wire connected toanother portion of an electrical circuit the device operates as aseparate potentiometer.

The device is not limited to be used as two separate rheostats or twoseparate Potentiometers. For example, assuming that terminal 20 isconnected to terminal 3a, the wires of the internal resistance assembly3a and 3b can act as a rheostat further varying the output of thepotentiometer formed by the outer resistance assembly and its brush orthe inner resistance assembly and the brush associated therewith can beused as a second potenticmeter in cascade or series relation to apotentiometer formed by the outer resistance assembly and its brush.

It will be appreciated that these various uses do not involve any changein structure of the device and while certain possible uses of which thedevice is thus capable without change, have been thus described it isnot to be inferred therefrom that such are the only uses. Moreover,while the resistance elements illustrated comprise three wires laid sideby side and wound helically in that condition, it is not to be inferredtherefrom that such windings are necessarily limited to the precisenumber and that either or both resistance assemblies may comprise anynumber of wires greater than one and that the windings do not have to beeach of the same number nor do they have to be wound in the samedirection. Moreover, while the contact portions of the brush componentsare here shown as comprising parallel wires yieldingly engaging thegrooves between adjacent ones of the convolutions comprising theresistance assemblies, the brush components need not be limited to beingformed from parallel wires and may be any metal contact means that willeffect the electrical shorting between adjacent convolutions which isessential to the operation of the device. The choice of wires for thisparticular use is primarily one of convenience. With the foregoingobservations in mind, it will be appreciated that the invention is notto be deemed to be limited to the precise details of construction andusage thus disclosed by way of example and that the invention includesas well all such changes and modifications in the parts and in theconstruction, combination and arrangement of parts as shall come withinthe purview of the appended claims.

I claim:

1. In a duplex, variable electrical resistance device, a base includinga resistance assembly support, first and second resistance assembliescarried by said support each comprising a plurality of elongatedelectrical conductors arranged in side by side relation and electricallyinsulated from each other throughout their lengths, and a pair ofseparate, manually operable means carried by said base, one of saidmanually operable means being associated with said first resistanceassembly and the other with aid second resistance assembly, each of saidmanually operable means including a resilient brush componentelectrically interconnecting the conductors of the one of saidassemblies with which it is associated at infinitely variable points inthe length thereof, one of said manually operable means additionallyserving as the support for the other of said manually operable means,means interconnecting said manually operable means effective to permittmovement of either of said manually operable means to effect variationof the associated resistance assembly while maintaining the thenexisting position of the other of said manually operable means withrespect to the resistance assembly with which said other manuallyoperable means is associated, and a plurality of terminals disposed onan exterior surface of said base connected one each to each of saidconductors and affording separate connection of the conductorscomprising said resistance assemblies into an electrical system, one ofsaid manually operable means serving in cooperation with said base toenclose said support and the resistance assemblies carried by saidsupport.

2. A duplex, variable electrical resistance device as claimed in claim 1in which said resistance assembly support comprises a hollow cylindricalsuppont, said support being mounted on said base and having one of saidresistance assemblies mounted on the external cylindrical surfacethereof and the other of said resistance assemblies mounted on theinternal cylindrical surface thereof.

3. A duplex, variable electrical resistance device as claimed in claim 2in which the one of said manually operable means associated with the oneof said resistance assemblies which is mounted on the exterior of saidsupport serves additionally in cooperation with said base to enclosesaid support and the resistance assemblies carried thereby.

4. A duplex, variable electrical resistance device as claimed in claim 1in which each of said resistance assemblies comprises a helix, and inwhich the associated manually operable means includes a brush componentrotatable about the axis of generation of the helix and which is movableas an incident to said rotation in a direction parallel to said axis.

5. A duplex, variable electrical resistance device as claimed in claim 2in which said resistance assembly disposed on the inner cylindricalsupport serves additionally as the supporting means for the brushcomponent which is in electrically conductive engagement therewith, inwhich said brush component is operatively connected to the one of saidmanually operable means which is supported by the other of said manuallyoperable means, and in which devices operated by the manually operablemeans which is supported by the other manually operable means areconnected to and effect movement of said brush component relative to thesaid resistance assembly on the inner surface of said support.

6. A duplex, variable electrical resistance device as claimed in claim 2in which the one of said manually operable means associated with theresistance assembly mounted on the outer surface of said support ismounted for rotation on said base and includes a component whichcooperates with said base to form a housing for said support and theresistance assemblies carried thereby and which, additionally, isoperatively connected to the brush component which is supported by andelectrically interconnects the conductors constituting said resistanceassembly disposed on the outer surface of said cylindrical support whilepermitting movement of said brush component in directions parallel tothe axis of said rotative movement.

7. A duplex, variable electrical resistance device as claimed in claim 3in which the one of said manually operable means associated with the oneof said resistance assemblies mounted on the inner cylindrical surfaceof said support is mounted for free rotation on the manually operablemeans associated with the resistance assembly mounted on the externalcylindrical surface of said support and which manually operable meanscooperates with said base to enclose the cylindrical support and theresistance assemblies carried thereby.

8. A duplex, variable electrical resistance device as claimed in claim 3in which the manually operable means associated with the resistanceassembly mounted on the outer surface of said support is detachablymounted for free rotation on said base to afford access to the interiorof said device.

9. A duplex, variable electrical resistance device as claimed in claim 3in which said manually operable means which encloses said support andresistance assemblies is provided with bearing engagement on theperiphery of said base and on said support at a point axially remotefrom said base.

References Cited by the Examiner UNITED STATES PATENTS 1,490,334 4/1924Lindberg 338126 2,065,805 12/1936 Harrison 338126 X 2,122,370 6/1938Harrison et al 338126 2,277,883 3/1942 Rich 338-131 X 2,548,591 4/1951Crowley 338126 2,724,034 11/1955 Altieri 338126 FOREIGN PATENTS 658,0673/ 1938 Germany.

ANTHONY BARTIS, Primary Examiner.

1. IN A DUPLEX, VARIABLE ELECTRICAL RESISTANCE DEVICE, A BASE INCLUDINGA RESISTANCE ASSEMBLY SUPPORT, FIRST AND SECOND RESISTANCE ASSEMBLIESCARRIED BY SAID SUPPORT EACH COMPRISING A PLURALITY OF ELONGATEDELECTRICAL CONDUCTORS ARRANGED IN SIDE BY SIDE RELATION AND ELECTRICALLYINSULATED FROM EACH OTHER THROUGHOUT THEIR LENGTHS, AND A PAIR OFSEPARATE, MANUALLY OPERABLE MEANS CARRIED BY SAID BASE, ONE OF SAIDMANUALLY OPERABLE MEANS BEING ASSOCIATED WITH SAID FIRST RESISTANCEASSEMBLY AND THE OTHER WITH SAID SECOND RESISTANCE ASSEMBLY, EACH OFSAID MANUALLY OPERABLE MEANS INCLUDING A RESILIENT BRUSH COMPONENTELECTRICALLY INTERCONNECTING THE CONDUCTORS OF THE ONE OF SAIDASSEMBLIES WITH WHICH IT IS ASSOCIATED AT INFINITELY VARIABLE POINTS INTHE LENGTH THEREOF,ONE OF SAID MANUALLY OPERABLE MEANS ADDITIONALLYSERVING AS THE SUPPORT FOR THE OTHER OF SAID MANUALLY OPERABLE MEANS,MEANS INTERCONNECTING SAID MANUALLY OPERABLE MEANS EFFECTIVE TO PER-